The present invention relates to a method and apparatus for brazing at least two metal members together in a brazing furnace using a substantially pure braze material, at least one of the metal members being nonplanar.
High energy neutral beam sources are gaining significant importance for plasma and other technologies. Neutral beams are particularly useful as a means for adding energy to the plasma in a confining device such as a fusion reactor.
A neutral beam is typically generated by accelerating ions to a desired energy level, and subsequently passing the ion beam through a low energy neutral gas background. Through the process of charge exchange, electrons from the background gas are passed to the high energy ions, thereby neutralizing the beam. More specifically, in an arc chamber assembly, a plurality of filament electrodes are energized to a temperature sufficient to emit electrons. The electrons collide with deuterium gas atoms which are bled into the arc chamber from a plenum chamber and the deuterium atoms are ionized as a result of the aforementioned collisions. The ionized atoms are accelerated to a potential of about 80 kV. The accelerated ions are subsequently neutralized and the neutralized ions drift through the magnetic field confining the fusion plasma to fuel the fusion reaction.
The arc chamber design requires that the deuterium gas be confined within the arc chamber volume. To achieve the desired operating pressures within the arc chamber, it is necessary that the arc chamber electrodes be fabricated in a manner that will retain the temper of the OFHC copper plates used for the electrodes. At the same time, it is necessary to provide a low vapor pressure, high thermal conductivity path between the OFHC copper coolant tubes attached to each of the electrode members to carry away heat generated by filament radiation, electron and ion bombardment and other power losses.
In the prior art, the copper coolant tubes were attached to the copper electrodes using a heliarc welding technique and fillers such as silver-copper brazing rods or copper-tin-phosphorous welding rods. However, because the OFHC copper electrodes are relatively thick and exhibit good thermal conductivity, it is necessary to employ very hot welding arcs to achieve adequate bonds and fillets using this material. As a result, considerable stress and warpage is induced in the copper assemblies joined by these methods. Thus it is desirable to find a method whereby copper cooling pipes may be attached to copper electrodes without inducing stress and warpage into the joined members.